woolridge



Jan. 24, 1956 H. I. WOOLRIDGE CAM PAWL. SHOCK ABSORBER Filed June 24, 1954 2 Sheets-Sheet l 46 J 35 C" ft? 7 7 IO 16 I4 I I [J a? Ha if INVENTOR.

HAROLD l. WOOLRIDGE ATTORNE) United States Patent 2,731,853 CAM PAWL SHOCK ABSORBER Harold I. Woolridge, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, :1 corporation-of Iowa Application June 24, 1954, Serial No. 439,114 6 Claims. (Cl. 74-569) This invention relates to means for absorbing the shock of a cam follower when it rides over an abrupt cam surface.

Conventionally, cams are often utilized to provide a controlled relationship between rotational and linear movement.

cam follower displacement.

A portion of the periphery of a cam, herein called the The remaining portion of the periphery, herein called the repositioning periphery, is used to reposition the follower pense of repositioning periphery, repositioning is done over a smaller portion ofaperiphery and accordingly becomes more abrupt.

In certain cases, it is required that a follower move smoothly over the control periphery from a low position Cams are used in radio tuning apparatus to actuate movable cores in tuning coils; and the cam is generally It is another object of this invention to provide means for increasing the life of a cam-follower combination that utilizes an abrupt change of periphery;

It is still another object of this invention to provide shock absorbing means which does not interfere with cam operation.

It is a further object of this invention to provide means which allows virtually all of the periphery of a cam to be used as control periphery.

It is a still further object of this invention to provide means which permits a cam to be designed with a radial' change in its periphery.

The invention provides a spring biased pawl which moves with a cam follower. The pawl is pivotally supent to a person skilled in the art upon further study of this specification and drawings, in which:

Figure 1 is an elevational view of the invention which used in explaimng the invention, as viewed along section.

4-4 inFigure 2.

Now referring to the invention in more detail, Figure 1 shows a side elevational viewof the invention as it is embodied in radio tuning apparatus.

fixed to "shaft ll-near its opposite ends 11(a and 11(b end to frame 10 and each container 14 supports-within it a tuning coil. 16 (not shown).

A pairof U-shaped guides 17 and 18 are fastened at Patented Jan. 24, 1956 A frame 10 rotatably supports acam shaft 11, and a pair of cams 12 and 13 are ingafollower- 31. A- projection 39 extends frorrr pawl 36 on the side of follower 31; opposite from the pivoted end 37.

Afirst'upper:supportblock 41*is fastenedto tuning plate 21*adj'acent-to openingiti' Acapped-pin 42 projects from block 41 over opening-26: and supports a;sp ring 43 which has L--shaped'ends 44" and"45 'that=extend'oppositely from pin-422 Sp'ring-end*44 engages the upper surface of "tuning plate 21, while the other, end 45 engages the upper side-of' pawl36'to bias itagainst stop-pin- 38.

Insi'milar manner; a second pawl-46iis pivotally'supported at one end 47 by the other lowersupport block 24' and-extends, in-part; through opening 27in tuning plate 21; A -stop-pirwl8 projects from block.24 andengages pawl 46 to prevent it from contacting follower 32:.

Also, a seconduppe'r' support block 51 is fastened to tuning plate 21 adjacent the other opening 27; A cappedpin=52 projects from block 51' over opening 27 'and'supports aspring 53 whichhas Lj-shaped ends 54 and 55 that extend oppositely from pin 52: Spring end 54engagesthe uppensurface of plate 21, and the other end 5S.engages the-upperside of pawl 46=to bias it against stop-pin 48;

Cam 12 is bestshown in-Figures'4('a) through (d). Its periphery 60'isformed generally with a spiral shape which extend'sfrom a low level 61to a high level 62. High level 6Z terminatesata precipice63 which initiates a drop-ofior radial portion 64-of periphery that-connects high level 62 tolow l'evel 6'1'and provides the repositioning periphery of cam-12; Cam 13 (not similarly shown) is identical. in shape and is aligned on shaft ll with cam 12.

The operation of cam 12 is described in detail with reference to drawings 4(a) through (d). Butit is understood that=the description of operation of cam 12 equally applies -to cam-13 since the cams and their adjoining parts areidentical. Accordingly, to avoid repetition, the operation of cam -13'is-not described in detail.

Cam shaft 11 is rotated clockwisein Figure 4. bymanual or mech'anical means. Let it be assumed thatfollower 31 is initially in the position shown in Figure 4(d). As cam lz rot-ates, follower'31 is displaced smoothly in a controlled. manner from the low position shown in Figure 4(d) where it -engages the low'level '61, Figure 4(a), where it engages high level. 62. During this period; follower 31- is actuated by and aprecise relationship is maintained between cam shaft. rotation and the displacement oftuning 2'1i'which rides with-follower31. Also-during this control period, frame. springs 33 and 34- areloaded, as tuning plate 2-1'is away from frame 10. Furthermore during this time, pawl 36-restsidly on-stop-pin 38 due to the bias'of pawl spring 43; and pawl '36 accordingly is maintained out'of engagement with-control periphery 60 and-cam-follower 31.

Eventually, is again ready to repeat a similar cycle-with control' periphery- 605 Figures 4(1)) and-4(a) showtransient. positions: of follower3l while it drops to low level 61'.

Springs-33 and 34 at all times provide tension on plate ll andmaintain follower 31 biased against the periphery of carn' 12, except possibly while it drops to low level 60;

In more detail, Figure 4(a) shows cam follower 31 as it reachesthe-end'of highlevel- 62 wherev itis about to. pass oven-preeipice-fiSJ it is 'noted that; at this-time; stop-pin 38 maintains the end portion 39 of pawl 36 out ofengagement with the=cam1peripheryr As cam 12 rotates further, follower :31 'passes over-precipice- 63 and begins to drop along-radial periphery 64. Very shortly, pawl portion 39 contacts precipice 63;

plate 21 dropswith follower prings, are l aded nrlthc. frame: prings: are-unloaded:

achpthertand prings to the high position shown the control periphery 60 moved follower- 31 passes over-precipice 63 and, drops radially along periphery 64- to low level 61 wlrterev it and pawl 36 pivots counterclockwise awayfromstop-pin 3810 load spring 43. However, tuning 31.,and springs 33 and.,34 tin-,- load." Thus during the, drop of. follower. 31, the;- pawlof'pawlfspring 43.

43 and 53 brake the fall. Eventually as follower 31 approaches very near to low" level 61; the opposing-forcesof the springs virtually neutralize each other, since at that point springs 43 and 53 are loaded to a maximum and springs 33 and 34 are unloaded to a minimum. Thus, when follower 31 contacts low level 61, there is very little net force on follower 31 and ve-ry-- little shock occurs. It

is therefore. apparent that a transfer of. energy occurs during the fall' from the frame springs to the pawl springs.

It will .be realized that the drop .of, followers; 31 and '32-. occursvery swiftly in relation to therotation ofi-the-cams', and they have rotated only a slight amount-whenfollower 31 contacts low level 61.

The energy released by the fall of the cam followers is uniformly dissipatcdduring and-after the fall by the sliding friction between pawl portion 39 and radial periphcry 63. After pawl 12 begins pivoting, portion 39 slides downwardly against radial periphery 64.under. the force Finally,- when. follower level 61; as shown in Figure 4(d), pawl 36 has pivotedtto. a maximum andstillis slideably engaging =radialperiplicry 64. As carn'12f rotates further, follower 31 rideson. control surface 60'alonglow1evel61 while pawl portion, 39' completes its frictional cyclewith. radial'periphery 64 to complete the dissipationofthe energy stored in the: pawl springs. Pawl36 then returnsto its normal position of rest againststop-pin 3.8.and isv heldoutofengagement with control periphery 60'. It is ready. to repeat its operation when ,thefollower; again .pass'e'slover precipice .63.

The, only time thatpawls 36 and 46, pawlv springs43 andj53are actuated is during the fall of the camfollowersand for theperiodl immediately following.

Virtually all of theenergy released by the fall is dis;

sipate'dby rubbing. which. occurs between pawl end. 39

and radial portion 64. Wear by these elements does not effect the accuracy of the cam controlfunction. I

Sincegfollower, 31 contacts, low level 61' with very little.

. force, the invention allows only a minimumof'wearto rotat'ably snpportedby said frame,v saidcams mounted. on... saidicamshafnatuningrplate, reciprocally supported from: saidframewith a pair of openingsformed. adjacent to i said. follower occur to follower 3Iand, to the level 61;

Roller typefollowers aroused. in this embodiment be! cause they minimize friction, however, Slidingtype foli lowersmay be used if.

required.

It is hence apparent that this invention providesmeans for absorbing the shock of acam follower whenit passes over, a large drop ofi'discontinuity inthelperipherycf a.

cam. Thelifeoi the. cam-follower combinationris in:

creasedaccordihgly. Also, the shock absorbingmeanstof this invention in noway'interferes with the operation ofz the cam; Furthermore, the. invention permitscarnsztobeutilized'which havealrnost 3,60,v degrees of controlperiplr. cry since it permits the repositioning periphery to bemade; radial. i

While a specific embodiment ofthe inventionhas been. described, .various changes and modifications. willlbe. ob.-.- O S fliQSflkilIed.inthetart which do not depart from the-spirit andfscope ofthe invention.

I claim; i v

l. Shock,absorbingmeansfQr a pair of cam followers, engaging respective camswhich havetsubstantially radialv repositioning peripheries and. smoothly varying. controlvv peripheries comprising, afr'ame member, a cam. shaft said carn's,'a pair oflower. blocks fixed tov said plate-.adn

iacenttosaid. 0penings,. a follower. shaft rotatably supported by said lower blocks, said. cam .followerssfixedito.

means connectedv maintain-said. followers in: engagement withgsaid. cams; a pivotally. supported, by said...lowerz:.bloclts:

pair of pawls respectively int lignmcnt Wiih:Sald'jOpQH 1[lgS, the: pivot 'fo owenwith;respectito..the;rotation 3.1, engages low:

control periphery at low haft to engage the respective-cams, spring between said tuning plate-and frame :to

of pawl projections extending from said pawls adjacent pawl pivotally supported by said follower supporting ach cam and follower, said projections located on the means, a stop pin fixed to said supporting means to ensupported by said capped pins and engaging the respec- 10 4. Shock absorbing means for a cam follower which tlve pawls to bias them against the stop pins engages a cam with a large abrupt drop 1n its periphery 2 Shock absorbing means for a cam follower WhlCh comprising, means suporting said cam follower, a pawl engages a cam with at least one abrupt change in pehaving a pro ectlon and pivotally supported by said riphery comprising, a frame member, a plate reciprocally means, means biasing said pawl pivotally toward the supported by said frame, a lower block mounted on said 15 periphery of said cam, and the projection of said pawl plate adjacent said cam, said follower rotatably supported located on the trailing side of said follower with respect to by said lower block to engage the periphery of said cam, the rotation of said cam. biasing means connected to said plate and said frame to 5. Shock absorbing means for a cam follower which bias said follower against said cam, a pawl pivotally supengages a cam with a large control periphery and a subported at one end by said lower block, said pivot located 20 stantially radial repositioning periphery comprising,

end to said upper block, and a spring supported by said 30 said pawl projection out of engagement with the control against said stop pin.

3. Shock absorbing means for a cam follower which References Cited m the file of am patent engages a cam with an abrupt drop in its periphery com- UNITED STATES PATENTS prising, means supporting said cam follower, means bias- 5 1,904,799 Palmer Apr. 18, 1933 ing said follower supporting means toward said cam, a 2,567,735 Scott Sept. 11, 1951 

